Peak Hill Project

Peak Hill is located 100km north of Meekatharra. Acquired from Westgold Resources in May 2026, Peak Hill is an historic gold field with a history of high-grade gold mining and more than 900,000oz of past production. The Project contains a 481,000oz JORC 2012 Mineral Resource across five deposits, with substantial near-term growth potential from resource extensions and known high-grade targets.With gold resources on granted mining leases and an Ore Purchase Agreement with Westgold, the Company aims to bring Peak Hill into production by the end of 2027.

Project highlights

481,000oz JORC 2012 Mineral Resource at 1.6 g/t Au across five deposits (ASX: 4 May 2026)

More than 900,000oz of historic gold production — including 680,000oz from Five Ways alone

Ore Purchase Agreement with Westgold Resources for processing at Fortnum (~50km), Bluebird or Tuckabianna mills

7 granted Mining Leases and 1 granted Exploration Licence covering 106km² in the Northern Murchison

Great Boulder is undertaking an aggressive program of resource definition and extensional drilling prior to bringing Peak Hill back into production by the end of 2027.

GBR’s Meekatharra projects — Peak Hill (north) and the 1Moz Side Well Gold Project (south), with Westgold’s regional processing infrastructure.

Peak Hill is located in the Murchison region 100km north of Meekatharra. The project is well positioned, surrounded by active mine sites, established infrastructure and access to multiple nearby processing facilities.

With a 106 km² tenement package, including granted Mining Leases over existing resources and open pits, the project covers the core of the Peak Hill greenstone-hosted, structurally controlled orogenic gold system.

Peak Hill currently hosts a 481,000 oz JORC 2012 Mineral Resource at 1.6 g/t Au across five deposits and has an additional Exploration Target of 600–740 koz.

Alluvial gold was first discovered at Peak Hill in 1892. Modern open-pit mining commenced in 1988 with the Mt Pleasant pit and finished in 1997 at the Harmony pit. There has been no mining at Peak Hill since that time.

Despite its rich history, the Peak Hill area has remained under-explored for more than 25 years, and this presents an enormous opportunity for Great Boulder to rapidly grow the current resource base and bring the project back into production quickly and at a low capital cost.

Great Boulder aims to complete at least 40,000m of RC and diamond drilling in the second half of 2026, after which the resources will be re-estimated and updated.

Peak Hill Gold Project — tenement overview showing the five JORC 2012 resource deposits and key prospects across the 106km² tenure.

Peak Hill comprises a series of structurally controlled orogenic gold deposits developed across Paleoproterozoic greenstone and metasedimentary sequences in the Northern Murchison. Mineralisation styles vary across the camp, reflecting different host rocks and structural settings, including the Peak Hill Schist at Five Ways, dolerite-contact mineralisation at Jubilee, and Narracoota Volcanics / Bryah Group sequences at Harmony, Enigma and Durack.

Gold mineralisation is typically associated with quartz veining, sulphides and structural/lithological contacts, with higher-grade shoots developed where favourable structures, host rocks and alteration zones interact. This variation in geometry between deposits is important, as it creates multiple target styles across the broader Peak Hill corridor.

The main geological opportunity at Peak Hill is the scale of the partly tested mineralised camp. Existing resources, historical workings, soil anomalism and shallow drilling define several open trends where mineralisation remains unconstrained along strike and at depth. Systematic drilling and updated geological modelling will provide a clear opportunity to refine the controls on mineralisation strong potential to improve geological understanding and define additional gold resources.

Peak Hill hosts five JORC 2012 resource deposits and several advanced exploration prospects across a 20km strike length of prospective greenstone stratigraphy. The combined Mineral Resource totals 9.4Mt at 1.6 g/t Au for 481,000oz. All five deposits are open along strike or at depth, and none has been drilled with modern systematic programs in recent years.

Five Ways is the largest and most productive deposit in the Peak Hill district, with historical production exceeding 680,000oz from combined open pit and underground operations. Mineralisation is hosted within the Mine Sequence of the Peak Hill Schist—a mylonitic quartz–muscovite schist of early Proterozoic to possibly Archaean age, metamorphosed during the Capricorn Orogen.

Gold mineralisation is controlled by a hierarchy of nested structures. A major NNE-trending shear zone bisects the deposit and controls the orientation of gold-bearing tension veins, while the Otway Fault Set defines mineralisation at the deposit scale. A conjugate NE–SW fault system further enhances fluid flow, localising high-grade ore shoots. Gold occurs in two main vein styles: fine tension veins within the shear zone and broader quartz veins (up to 1 m wide) parallel to schistosity, both associated with strong biotite alteration.

The mineralised system extends over 1.4 km of strike and to at least 310 m depth, yet drilling has not tested below ~200 m vertical depth. Mineralisation remains open down-plunge to the west and along strike to the north, where drilling is sparse beyond the current pit limits. These extensions represent a key focus of the 2026 drilling program.

View of the Five Ways pit looking northwest

Jubilee is the highest-grade deposit in the current resource at 2.3 g/t Au, located 2 km north of Fiveways along the same NNE-trending structural corridor. In contrast to Five Ways, mineralisation is hosted at the contact between the Hangingwall Sequence of the Peak Hill Schist and an intrusive meta-dolerite dyke, forming a quartz stockwork system that produces shallow north-dipping lodes which flatten away from the intrusive margin.

Immediately west of the main resource, historic underground workings (Golden Treasure, Golden Treasure East and Emerald) targeted a second, high-grade mineralisation style comprising steeply dipping, NE-striking reverse fault veins. Recent drilling completed by West Gold in 2025 within this “Treasure corridor” returned significant intercepts, including 10 m at 18.79 g/t Au and 19 m at 13.34 g/t Au, confirming a high-grade structural system not yet incorporated into the current resource.

The dolerite contact wraps around the eastern and northern margins of Jubilee, with the resource extending onto lightly tested ground to the northwest. Importantly, the 2 km corridor between Jubilee and Fiveways remains largely untested, despite widespread gold-in-soil anomalism and shallow RAB results—representing one of the most compelling near-term growth targets within the project.

Harmony is hosted at the stratigraphic contact between the Narracoota Volcanics—mafic-ultramafic lavas and tuffs of the Bryah Group—and the overlying Thaduna greywacke sediments, interpreted as a thrust contact. Gold mineralisation is concentrated within the Narracoota basalts immediately above this surface, while the Thaduna sediments are largely barren.

Mineralisation is structurally complex, comprising an en-echelon vein system developed across three key orientations. NE-trending tension veins represent the primary mineralised set, linked to a major ENE shear zone south of the deposit. Secondary ESE–WNW pressure faults and a WNW-trending bounding structure further control vein geometry, with high-grade shoots forming at structural intersections. Importantly, the controlling ENE shear is interpreted to extend eastward toward Fiveways, suggesting a district-scale mineralised corridor across largely untested ground.

Harmony has been previously mined via open pit and remains open to the north, where approximately 100 m of untested strike persists beyond current drilling. With a resource grade of 1.9 g/t Au and close proximity to the Fortnum access road, Harmony represents a compelling near-term ore source under the Westgold ore purchase framework.

Enigma is hosted within the Narracoota Volcanics of the Bryah Group mafic–ultramafic sequence, 3 km southeast of Harmony, and is structurally controlled at the hinge of a regional anticline. Gold occurs in moderately to steeply west-dipping quartz–sulphide veins, representing a more sulphide-rich and structurally focused style than the shallower tension veins at Harmony, reflecting the influence of fold-hinge geometry.

The Enigma trend extends over 5 km of strike, with higher-grade mineralisation concentrated at Enigma North. The current 41 koz resource represents only the most densely drilled portion of the system, while southern extensions remain largely untested, defined by wide-spaced RAB traverses (~500 m line spacing) and limited RC drilling (four holes since 2010). With no historical mining, Enigma remains the most underexplored resource deposit in the Peak Hill district.

The interaction between the anticline hinge and the ENE shear at Enigma North creates a focused structural setting with strong potential for higher-grade shoots at depth. Modern oriented RC and diamond drilling has not yet been applied and is expected to significantly improve geological understanding and resource definition across the system.

Durack and its satellite Windsor lie 13 km south of Five Ways within steeply north-dipping Narracoota Volcanics and volcanogenic sediments of the Bryah Group. Mineralisation is structurally controlled by the WNW-striking Durack Shear, a major hydrothermal corridor hosting discontinuous quartz veining and alteration.

Durack is the second-largest resource by contained ounces and the largest by tonnage outside Fiveways. Neither Durack nor Windsor has been mined, with both representing open-pittable systems. Windsor exhibits steeper vein dips (65°N), suggesting structural variation within the same hydrothermal system. The resource was modelled using Multiple Indicator Kriging due to vein discontinuity, with significant potential for refinement through modern oriented drilling.

The Durack Shear extends at least 1.7 km northwest beyond the resource to Murphy Creek, where anomalous RAB results remain untested by RC drilling, defining a compelling open-ended exploration corridor.

The table below reflects the resource as reported on 4 May 2026.

Reported at variable cut-off grades by deposit. Tonnes in thousands (kt). Source: GBR ASX Announcement, 4 May 2026. Subtotals rounded.

Peak Hill remains significantly underexplored, with five deposits defined across ~20 km of strike, yet only limited application of modern exploration techniques. The current resource footprint represents only a small portion of the broader geological potential.

Great Boulder has applied the same systematic exploration approach that expanded its flagship Side Well Project to over 1 Moz, integrating gold-in-soil anomalism, historic RAB and RC drilling, and geophysical datasets to identify multiple untested targets across the tenure.

The 2026 program—comprising up to 60,000 m across Peak Hill and Side Well—is designed to systematically test these opportunities for the first time, including:

  • Five Ways down-plunge: 680,000 oz system never drilled below ~200 m vertical depth, with open plunge continuity into fresh rock; RC/diamond drilling is a priority.
  • Jubilee–Five Ways corridor: 2 km largely undrilled structural gap, with soil and RAB anomalism indicating continuity of the mineralised system.
  • Enigma 5 km trend: 41,000 oz resource sits within a broader 5 km anomaly; only four RC holes drilled since 2010 with strong strike-extension potential.
  • Murphy Creek (Durack North): 1.7 km along strike from Durack resource, with untested anomalous RAB results defining a potential corridor extension.
  • Mt Pleasant & Treasure: Undeveloped prospects along key structural trends, including the Jubilee corridor; both remain untested to resource definition level.
  • Geophysical targets: Multiple untested magnetic and gravity anomalies defining structural nodes and lithological contacts across the tenure.